Vacuum pump
a vacuum pump and vacuum technology, applied in the direction of motor/generator/converter stopper, dynamo-electric converter control, instruments, etc., can solve the problems of easy distortion of sensor signals and increase in costs, and achieve the effect of preventing the increase in the cost of the device and improving the accuracy of temperature determination
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first embodiment
[0032]FIG. 1 shows the first embodiment of a vacuum pump according to the present invention. This figure shows the arrangement of a pump main body 1 and a controller 30 of a magnet-bearing type turbo-molecular pump. A shaft 3 having a rotor 2, is supported without direct contact with electromagnets 51, 52, 53 that are provided in a base 4. A surfacing position of the shaft 3 is detected by radial displacement sensors 71, 72 and an axial displacement sensor 73 provided in a base 4.
[0033]A circular disk 41 is provided at the lower end of the shaft 3. The electromagnet 53 is provided in such a way as to sandwich the disk 41 from both above and below. The shaft 3 is suspended in an axial direction by attracting the disk 41 using the electromagnet 53. The disk 41 is fixed to the lower end portion of the shaft 3 by a nut 42 which rotates integrally with the shaft 3. Magnetic body targets 81, 82 are provided in this nut 42.
[0034]On the stator side, which is opposed to the nut 42, a gap sen...
second embodiment
[0091]In the first embodiment, as shown in FIGS. 5(a), 5(b), in the case wherein the sensor output signals S2, when the gap sensor 44 is opposed to the magnetic body targets 81, 82, become smaller than the threshold as shown by the signals S2′, the rotor temperature monitor signals are output.
[0092]However, with the temperature change, the shaft 3 wherein the nut 42 is fixed by thermal expansion extends axially, and dimensions of the gap between the magnetic body targets 81, 82 and the gap sensor 44 change. Also, due to the change of the surfacing position of the shaft 3, the dimensions of the gap change. As a result, in spite of the magnetic permeability of the magnetic body targets 81, 82 remaining unchanged, the signals S2 change to the signals S2′ due to the change of the dimensions of the gap, so that the temperature T can be mistakenly determined to exceed the Tc.
[0093]Also, as shown in FIG. 4(a), the magnetic permeability in the case of T>Tc differs greatly from the magnetic ...
modified example 1
[0101]FIGS. 13(a) and 13(b) depict a modified example 1 of the second embodiment, and show nut 42 wherein the magnetic body target 81 is provided. There is a level difference with a height of h on the bottom face of nut 42, and the magnetic body target 81 is provided on the fixed surface 42a which is the higher side of the level. If nut 42 with the above-mentioned shape is used as a sensor target, when the rotor is rotated once, the sensor output as shown in FIGS. 14(a), 14(b) can be obtained. FIG. 14(a) shows the case of Tb) shows the case of T>Tc.
[0102]When nut 42 is opposed to magnetic body target 81, the sensor output becomes a signal S20 in the case of TTc, the magnetic permeability changes and the level declines as a signal S21. Also, in the case wherein the gap sensor 44 is opposed to a fixed surface 42b, the size of the gap becomes larger just by the level difference size h compared to the case wherein the gap sensor 44 is opposed to the fixed surface 42a. Accordingly, a sig...
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